1. Field of the Invention
The present invention relates to a vehicle steering device in which both the front wheels and the rear wheels are steered.
2. Description of Relevant Art
U.S. Pat. No. 4,295,657, issued on Oct. 20, 1981 to the present applicants, discloses a vehicle steering device in which the front wheels and the rear wheels are steered under a steering operation of the steering wheel. The vehicle steering device is constructed such that the rear wheels are steered in the same direction as that of the front wheels when the steering wheel is rotated a small angular extent, such as generally occurs during high speed driving of the vehicle, and to the contrary, during large angle steering operation of the steering wheel when driving at a low vehicle speed, the rear wheels are steered in a direction opposite to that of the front wheels or a rear wheel steering angle is reset to zero or to a value near zero. Thereby, a difference in time for producing lateral forces in the front wheels and the rear wheels is eliminated, non-coincidence between the direction of the vehicle and the tangential direction of the turning orbit is eliminated and at the same time a steering characteristic for the vehicle during high speed driving is improved, and rotating performance of the steering wheel during low speed driving of the vehicle is also improved or is facilitated to such a degree as to be similar to that provided by a conventional type of vehicle in which only the front wheels are steered.
In a conventional type of vehicle, the rear wheels are normally suspended by a suspension mechanism comprising a shock absorber, lower arms, etc., in such a manner as to be capable of swinging in a vertical direction. However, it is sometimes necessary to shorten the lower arms in response to a characteristic of the suspension desired in the suspension mechanism, and in this case, in a device in which the rear wheels are steered along with the front wheels, the length of the right and left tie rods for use in steering the rear wheels is also shortened and the opposing ends of both tie rods are spaced apart. As a result, the rear wheel steering means is required to be installed between the tie rods in the width or transverse direction of the vehicle.
The present invention provides a steering device which effectively meets the foregoing requirements.